The present invention relates to the field of sensors for converting various physical quantities into electrical signals, and more particularly relates to a particular construction for such a sensor.
In the prior art, many known sensors have been constructed for sensing various physical quantities such as temperature, pressure, vibration, and the like, for automatic control and measurement in various mechanical devices, such as, for example, automobiles, and these sensor elements are generally contained in enclosed spaces within protective casings made of metal or plastic, so as to prevent ingress of moisture, oil, dust, or other undesirable pollutants thereinto. However, the problem of ingress of oil, dust, moisture, or the like into such sensors is still not completely solved, especially if it is required to produce the sensor fairly cheaply, and to make it compact.
In particular, a sensor which is to be attached to an automobile engine is subject to very severe conditions, such as change of temperature, vibration, attack of oil, water, mud, dust, noxious gases, and the like. Therefore, the casing of such a sensor to be attached to an automobile engine must be particularly sealed against such environmental hazards.
Further, since such sensors produce electrical output signals which indicate the value of the physical quantity which they are measuring, electrically conducting lead wires must be connected to their sensor elements for transmitting the output electrical signals generated in these sensor elements. Most small size sensors are generally provided with a screw thread upon their outer cicumference, for mounting to the body of which a condition is required to be sensed. Such a form of screw attachment for a sensor is simple and convenient, and has the advantage that no special tool is required to mount the sensor to the body, but a disadvantage is present therein, in that, since the sensor casing needs to be rotated in order to screw it properly into the threaded hole in the body whose condition is required to be sensed, these electrical lead wires leading from the sensor casing will become twisted, and may be broken or tangled, and may exert force upon the sensor element mounted within the sensor casing, thereby disturbing the characteristics and the reliability of the sensor element and reducing the life of the sensor.
Further, in the particular case of the construction of a sensor element which senses vibration in a solid body, such as detonation, knocking, or pinging in an automobile internal combustion engine, and which is attached thereto by an attaching portion such as a screwed portion, problems have arisen with respect to the provision of a cheap and simple, yet reliable, construction arrangement for such a sensor, which can provide a sensor of long life and durability, and yet which is not extremely expensive or troublesome to manufacture, and which is not unduly bulky or weighty.
Further, especially in the case of a vibration sensor to be used on an automobile engine, the provision of electrical connections for electrical lead wires to be connected to the sensor element has sometimes been prone to poor contacting and other malfunctions, or to entry, over a long period of time, of water, dust, oil, or other contaminants into the connecting portions between said lead wires and the sensor.